investigating Thrust to weight ratio: confused

[Top Jockey]

21 minutes ago, Spurts said:

CL max for the F-14 is ~2.2. 

 

If you run the equation for induced drag it is D_i=C_Di*q*S. (q is dynamic pressure, 0.5*rho*V²)

C_Di=C_L²/pi*e*AR (e is the Oswald's Efficiency Factor and measures how elliptical the lift distribution is across the span, we will largely ignore this for now)

C_L=n*W/q*S

We will ignore stability impacts on n for the moment

C_Di=n²*W²/q²*S²*pi*e*AR

AR=b²/S (b is Wingspan)

C_Di=n²*W²/q²*S*pi*e*b²

If we fold this back into induced drag and simplify we get

Di=n²*W²/q*b²*pi*e

Let's call n²/q*pi*e "K" as this will assume same G, Speed, Altitude, and Oswald's efficiency factor

Di=K*W²/b²  

So we can see that the driving force for drag due to lift is span loading, not wing loading.  Stability plays an equal part but makes the computations much uglier.

F-14A and B have slightly lower Span Loadings when loaded (4AIM-9s and 4-AIM-7s vs 4R-73s and 2R-27s) and at matching fuel fractions (20%).  Assuming they have equal stability this pans out.  Long straight wings tent to have better e than swept trapezoidal wings so the e value in the equation lends itself more to the F-14 advantage as well.

 

In the end though this is about T/W ratios.  Thrust drops ~15-20% on installation, increases with airspeed, and drops with altitude.  Different engines perform differently at different regimes and in different airframes (inlet design and function matters).  A J79-GE-10 installed in an F-4 makes more thrust at 2.0M and 35,000ft than an F110-GE-129 installed in an F-16 at the same flight condition.  A higher T/W on paper does NOT mean better acceleration under a given regime in flight.  

 

You see this in cars too.  I had a truck with 305hp, 380lb-ft of torque, a 5-speed transmission, a 3.55 rear axle, and weighed 5200lb.  I had an SUV with 255hp, 330lb-ft of torque, a 4-speed transmission, a 3.42 rear axle, and weighed 6100lb.  On paper it shouldn't even be close, but the SUV had better straight line performance across the board.

 

 

Thnk you @Spurts for the insight.

I suppose in the F-14's case, the "pancake" area between engines would also help in its CL max ?

 

Searching through the web, I've found the following CL max values:

MiG-29A: 1.50

Su-27S: 1.85

F-15C: 1.60

 

And they all look too low when compared with the F-14.

Does anyone confirm these values ?

Edited December 8, 2021 by Top Jockey

[captain_dalan]

2 hours ago, Top Jockey said:

 

1 - By the way, which was the internal fuel (in lbs) in the MiG ?

2 -  Going straight to the point, my issue is:

I have some difficulty bearing my mind around that (the bold), as I always thought that in Real Life the F-14A variant (which is one of my very favorite jets), would be somewhat inferior to the MIG-29 in all of those speed ranges, turn-rate wise.

The F-14B variant, I can fully understand that would be a more than a match for the Fulcrum ACM wise, but the F-14A ?

I mean - even the pilots qualified it as completely under-powered because of its TF30 engines... ?

 

3 -

- empty weights:  the F-14A is almost twice heavier than the MiG-29A;

- Thrust / Weight ratio:  is better on the MiG-29A;

- Wing loading:  is better on the F-14A;

- Lift coefficients (CL max):  no idea which is better, I've read the MiG-29A's is supposedly 1.5 or something...

4 -

Several people here have explained to me that I've most likely over-valued the Fulcrum's real life ACM (BFM, dogfighting, whatever) turning capabilities, particulary against the Su-27 for instance, because:

" MiG-29 is a stable design, it's elevators acts opposite to wings decreasing it's overall lift, this increases AoA in turn (plane needs higher AoA for given G, thus bigger drag) and cause MiG to lose it's speed in turn faster than modern unstable designs like F-16 or Su-27. "

 

1 - Sorry, i forgot to include the number, despite writing the text. It was 6100lbs. Edited the post accordingly. 

2- Why do you think lack of power results in worse turning capability? WW1 biplanes are woefully underpowered and they can turn inside their own tails until they run out of fuel. Gliders have no power of their own at all, and can out-turn anything in the air.  If you've seen the performance charts for the F-14A and F-14B, you'd see that despite the tons of excess power the B has when compared to the A (manifested in superior acceleration, climb rates, loaded climbs...) their turning rates are barely 1/2 a degree different at the point of equilibrium (no excess power, level sustained turns). Is more power better? Yes, but in virtually every set of aerodynamic data i have ever seen, the alpha induced drag (drag as a result of increase in the angle of attack) rises faster (in a non linear fashion) beyond a certain point (around which the lift-to-drag ratio is optimal for a sustained turn) then ANY increase in thrust you might get as a result of a new more powerful engine. So even if you have 30-50% more thrust, you might get 10% or less excess power, as the increase in drag will just chew up the power. 

3- If you are really that interested, Clmax for the F-14 (without maneuver devices) is a bit more then 1.9 but it will do you no good in this case. All the properties you have listed above are next to useless when comparing dynamic conditions, even fairly predictable values, such as zero excess power turn rates. Let me put it this way (as this is my favorite example), a jest engine (just the engine) can have a thrust to weight of 8 to 1, or even 10 to 1, or above. Where is that engine going to go without wings, or fuel, or control surfaces, or someone or something to control those surfaces?  You CAN'T determine turn rates based on static values. You need the CL and CD values for all angles of attack available at given mach numbers AND you need the ACTUAL thrust produced at that given angle of attack and mach. Only by matching these two sides (lift-to drag per alpha and thrust to weight per mach) will you get the sustained g (or turn rate, really the same thing) for a given and state. And that will give you just that, the STR, which is by no means the end-all, be-all of turning capability as:

4- You are assuming that higher STR is better. Which it is, but only in a bubble, that is, if all other properties are the same. But they aren't. And while fighting at best STR has its uses, 9 times out of 10, the guy who fights at best STR, even if that STR is better  then the bandit's STR, will get thrashed by the guy who fights the proper energy exchanges. 
Let me put it this way:
-you fly at 350 knots and hold 6g until the heat-death of the universe;
-i can only sustain do 5g at 350 knots => you assume you are safe and continue to fly that way;
-but, even though i can only sustain 5g at 350, or 6g at 400, i can still do 7g at 350 and 8g at 400;
-aha you say, but you can't sustain them and i have made this a guns only fight!
-so what i say, and proceed to pull 8g. I can't sustain them, but i don't care. As a result i lose airspeed, my circle tightens and now i am not just inside your turn, i also have my nose on you. In case you haven't noticed, this is how the Mirage 2000 guys will shoot you on a dogfighting server. 
-ok you say, but what if you miss, you are now at 250, and you can't stay behind me for a long time, as you just can't sustain my rates! I got you again!
-so what i say? Who ever said i have to stay at 250? Because my plane is better then yours in acceleration, i can just unload, and get my knots back i a few seconds. IF i can get my knots back BEFORE you manage a full 360 to get behind me, i can do the same trick from above again and again, until i do get my shot. 
- Alternatively, i can even take the fight into the vertical, and cut my effective turn radius thus staying inside you circle even though you are rating with the speed of heat until you run out of fuel, and i can just keep bouncing you with high Yo-Yo's until you are dead. (this is less likely to see in DCS for the reasons i mentioned above, that is, maintaining tally is a pain in the butt)

Bottom line, i have out-turned you, even though my STR is worse then yours. For all intents and purposes, my EFFECTIVE turn rate is better, because i have exploited my plane's energy-properties better then you have. While you have kept your plane in a state of equilibrium the entire fight, i have traded energy for position, then position for energy and ended up with more shooting opportunities then you have. They key to success is knowing where in the envelope your best exchange rates are (what angle of attack, what mach numbers, what altitudes....)

EDIT: ah, isee @Spurts gave a good breakdown of the F-14's aerodynamic properties! 

Edited December 8, 2021 by captain_dalan

[Dell_Murrey-RUS]

3 часа назад, Top Jockey сказал:

Sure, but my point was the Su-27's "direct link control" can always allow for a "lightning quick" pitch rate (nose pointing) capability for a gun or missile snap-shot, that other fighters can not equal...( Obviously to be used in rare situations i imagine, as it would require a lot of skill, reflexes, aim from the pilot, and with the corresponding speed / energy loss. )

"direct control" - this is an emergency mode if all 4 channels fail in longitudinal control. And the activation of this mode is permissible up to speeds below 600 km/h.

"lightning quick" - this is very simple thinking. In fact, a very big question is the weight of the aircraft (fuel, rockets on pylons, position in space) and the capabilities of the sighting system for launching missiles. The gun mount is even more difficult. Shooting from it is highly discouraged at an overload of more than 4 g. Because it can jam. And even more so it is incredibly difficult to aim the gun with such a maneuver. The system may not have time to calculate the aiming mark of the target.

No one would risk an expensive fighter jet and give pilots such an opportunity. The probability of success in this situation is clearly below 25%, which is very very small. It is much more efficient to solve problems at long and medium distances.

3 часа назад, Top Jockey сказал:

Regarding the MiG-29A's damper I've tweaked with it some time ago, but does it allow for a pitch rate nearly as quick as the Su-27's "direct link control" ?

Well, no one forbids you to check it yourself. But from a scientific point of view, gliders with statically unstable in the longitudinal channel will give more gain over gliders built according to the classical design.

3 часа назад, Top Jockey сказал:

But if there's R-73 Archer missiles involved, many fights will not last much.

The R-73 is certainly a pretty good rocket. And it is especially dangerous for fighters in which the shooting of false IR traps is directed downward from the engines, which actually makes the air defense of such a fighter weak in air battles.

For Su-27 and MiG-29, launches of such missiles are less dangerous, because IR traps obscure the heat trail of engines and afterburners. If the pilot manages to clean up the engines from the afterburner to the maximum mode with the shooting of IR traps, then the missile will miss with a high probability. And if you reset the engine mode for 2-4 seconds to 90-85% along with shooting IR traps, then the rocket is guaranteed to miss. I consider only melee missiles dangerous if they do not show the smoky trail from the engines. This makes it difficult for the pilot to record the fact of the missile launch and the inclusion of the defensive complex.

3 часа назад, Top Jockey сказал:

In the end, I will ask you the same question I asked to Ironhand:

Would you qualify the Su-27S as a better dogfighting airframe than the MiG-29A, or not at all ?

Su-27 better.

[Cmptohocah]

1 hour ago, captain_dalan said:

...

Bottom line, i have out-turned you, even though my STR is worse then yours. For all intents and purposes, my EFFECTIVE turn rate is better, because i have exploited my plane's energy-properties better then you have. While you have kept your plane in a state of equilibrium the entire fight, i have traded energy for position, then position for energy and ended up with more shooting opportunities then you have. They key to success is knowing where in the envelope your best exchange rates are (what angle of attack, what mach numbers, what altitudes....)

EDIT: ah, isee @Spurts gave a good breakdown of the F-14's aerodynamic properties! 

 

This is simply not true for a two-circle fight. If you are below your max sustained turn rate (let's forget about corner speed for now), the adversary will get its nose on you eventually - it's just geometry. If you trade KNOTS for angles, there is absolutely no reason for the enemy to keep sustained turn rate and they too will trade speed for angles, but now they have more energy then you. Best you can do in this situation is try to force a one-circle fight or an overshoot, but this is not likely to happen with Archers.

[Top Jockey]

1 hour ago, captain_dalan said:

1 - Sorry, i forgot to include the number, despite writing the text. It was 6100lbs. Edited the post accordingly. 

2- Why do you think lack of power results in worse turning capability? WW1 biplanes are woefully underpowered and they can turn inside their own tails until they run out of fuel. Gliders have no power of their own at all, and can out-turn anything in the air.  If you've seen the performance charts for the F-14A and F-14B, you'd see that despite the tons of excess power the B has when compared to the A (manifested in superior acceleration, climb rates, loaded climbs...) their turning rates are barely 1/2 a degree different at the point of equilibrium (no excess power, level sustained turns). Is more power better? Yes, but in virtually every set of aerodynamic data i have ever seen, the alpha induced drag (drag as a result of increase in the angle of attack) rises faster (in a non linear fashion) beyond a certain point (around which the lift-to-drag ratio is optimal for a sustained turn) then ANY increase in thrust you might get as a result of a new more powerful engine. So even if you have 30-50% more thrust, you might get 10% or less excess power, as the increase in drag will just chew up the power. 

3- If you are really that interested, Clmax for the F-14 (without maneuver devices) is a bit more then 1.9 but it will do you no good in this case. All the properties you have listed above are next to useless when comparing dynamic conditions, even fairly predictable values, such as zero excess power turn rates. Let me put it this way (as this is my favorite example), a jest engine (just the engine) can have a thrust to weight of 8 to 1, or even 10 to 1, or above. Where is that engine going to go without wings, or fuel, or control surfaces, or someone or something to control those surfaces?  You CAN'T determine turn rates based on static values. You need the CL and CD values for all angles of attack available at given mach numbers AND you need the ACTUAL thrust produced at that given angle of attack and mach. Only by matching these two sides (lift-to drag per alpha and thrust to weight per mach) will you get the sustained g (or turn rate, really the same thing) for a given and state. And that will give you just that, the STR, which is by no means the end-all, be-all of turning capability as:

4- You are assuming that higher STR is better. Which it is, but only in a bubble, that is, if all other properties are the same. But they aren't. And while fighting at best STR has its uses, 9 times out of 10, the guy who fights at best STR, even if that STR is better  then the bandit's STR, will get thrashed by the guy who fights the proper energy exchanges. 
Let me put it this way:
-you fly at 350 knots and hold 6g until the heat-death of the universe;
-i can only sustain do 5g at 350 knots => you assume you are safe and continue to fly that way;
-but, even though i can only sustain 5g at 350, or 6g at 400, i can still do 7g at 350 and 8g at 400;
-aha you say, but you can't sustain them and i have made this a guns only fight!
-so what i say, and proceed to pull 8g. I can't sustain them, but i don't care. As a result i lose airspeed, my circle tightens and now i am not just inside your turn, i also have my nose on you. In case you haven't noticed, this is how the Mirage 2000 guys will shoot you on a dogfighting server. 
-ok you say, but what if you miss, you are now at 250, and you can't stay behind me for a long time, as you just can't sustain my rates! I got you again!
-so what i say? Who ever said i have to stay at 250? Because my plane is better then yours in acceleration, i can just unload, and get my knots back i a few seconds. IF i can get my knots back BEFORE you manage a full 360 to get behind me, i can do the same trick from above again and again, until i do get my shot. 
- Alternatively, i can even take the fight into the vertical, and cut my effective turn radius thus staying inside you circle even though you are rating with the speed of heat until you run out of fuel, and i can just keep bouncing you with high Yo-Yo's until you are dead. (this is less likely to see in DCS for the reasons i mentioned above, that is, maintaining tally is a pain in the butt)

Bottom line, i have out-turned you, even though my STR is worse then yours. For all intents and purposes, my EFFECTIVE turn rate is better, because i have exploited my plane's energy-properties better then you have. While you have kept your plane in a state of equilibrium the entire fight, i have traded energy for position, then position for energy and ended up with more shooting opportunities then you have. They key to success is knowing where in the envelope your best exchange rates are (what angle of attack, what mach numbers, what altitudes....)

EDIT: ah, isee @Spurts gave a good breakdown of the F-14's aerodynamic properties! 

 

 

Thank you for the highly detailed insight - very good.

 

2. I suppose more power is important to overcome drag also when turning > gaining / maintaining a little bit more speed on that turn > allow for pull more on the stick and maintaining more G's at a given speed ?

(... and the jet which can pull more G's for the same speed than the other, will have a superior turn rate.)

 

3. Fully understand the majority of the technical aspects you mention, although indeed I wasn't much aware of the " lift-to drag per alpha " aspect's importance.

 

4. on the Sustained Turn Rate :

- I do not think the STR is the "be all and end all" of ACM, (although is a parameter that catches my attention), if I thought I would be talking almost always exclusivelly about the F-16 here ;

- instead, regarding the MiG-29A, the STR is an aspect where I was expecting it to be stronger, given the characteristics I mentioned at the other post.

 

I guess, if the MiG-29A was instead an unstable design / relaxed static stability like the F-16, some aspects of its performance would be better... and amongst several details, it would have to get its center of gravity moved further aft, get a FBW, etc.

 

The several aspects I mentioned at the previous post, pertain to the following:

Supposing other important parameters being similar, wouldn't an airframe with a lower wing loading and better lift coefficient allow for maintaining more G's while turning, for the same speed, than a 'inferior' airframe ?

Edited December 8, 2021 by Top Jockey

[Top Jockey]

54 minutes ago, Dell_Murrey-RUS said:

"direct control" - this is an emergency mode if all 4 channels fail in longitudinal control. And the activation of this mode is permissible up to speeds below 600 km/h.

"lightning quick" - this is very simple thinking. In fact, a very big question is the weight of the aircraft (fuel, rockets on pylons, position in space) and the capabilities of the sighting system for launching missiles. The gun mount is even more difficult. Shooting from it is highly discouraged at an overload of more than 4 g. Because it can jam. And even more so it is incredibly difficult to aim the gun with such a maneuver. The system may not have time to calculate the aiming mark of the target.

No one would risk an expensive fighter jet and give pilots such an opportunity. The probability of success in this situation is clearly below 25%, which is very very small. It is much more efficient to solve problems at long and medium distances.

Well, no one forbids you to check it yourself. But from a scientific point of view, gliders with statically unstable in the longitudinal channel will give more gain over gliders built according to the classical design.

The R-73 is certainly a pretty good rocket. And it is especially dangerous for fighters in which the shooting of false IR traps is directed downward from the engines, which actually makes the air defense of such a fighter weak in air battles.

For Su-27 and MiG-29, launches of such missiles are less dangerous, because IR traps obscure the heat trail of engines and afterburners. If the pilot manages to clean up the engines from the afterburner to the maximum mode with the shooting of IR traps, then the missile will miss with a high probability. And if you reset the engine mode for 2-4 seconds to 90-85% along with shooting IR traps, then the rocket is guaranteed to miss. I consider only melee missiles dangerous if they do not show the smoky trail from the engines. This makes it difficult for the pilot to record the fact of the missile launch and the inclusion of the defensive complex.

Su-27 better.

 

Very good, including details I didn't know.

Didn't imagine the Su-27's gun could jam if shot when pulling over 4 G's.

 

Well regarding the bold... you leave no room for doubts.

I guess the more modern and refined aerodynamic design / each airframe's different stability concept / and a ton of aspects mentioned at the Russian forum thread last year, eventually do effect in each airframes performance.

Thank you.

[Cmptohocah]

31 minutes ago, Top Jockey said:

Supposing other important parameters being similar, wouldn't an airframe with a lower wing loading and better lift coefficient allow for maintaining more G's while turning, for the same speed, than a 'inferior' airframe ?

 

I am not sure about the wing loading, but max. sustained turn rate happens when the drag (mostly induced) and available thrust equalize.

[Top Jockey]

15 minutes ago, Cmptohocah said:

I am not sure about the wing loading, but max. sustained turn rate happens when the drag (mostly induced) and available thrust equalize.

 

I would say, there's 2 equal airframes (the same wings), but one has to lift less weight than the other, it would allow for doing a tighter turn ?

Edited December 8, 2021 by Top Jockey

[Spurts]

2 hours ago, Top Jockey said:

 

 

And they all look too low when compared with the F-14.

Does anyone confirm these values ?

 

Those are the values I have seen for the Su-27 and the F-15.

As for why they are "too low"?

Long straight wings are better at making lift (the whole reason for the swing wing) and the F-14 has full span leading and trailing edge high lift devices.  

Don't fall into the trap of "but muh pancake".  Flanker and Fulcrum have it too, and they both have LERXs.  F-15s inlets nod with AoA and act similar to Su-33 canards in managing the airflow over the broad, flat, lift making body.  Does the Pancake make lift?  YES!  But the AoA where it becomes effective is as/after the wings stall.

[Top Jockey]

31 minutes ago, Spurts said:

Those are the values I have seen for the Su-27 and the F-15.

As for why they are "too low"?

Long straight wings are better at making lift (the whole reason for the swing wing) and the F-14 has full span leading and trailing edge high lift devices.  

Don't fall into the trap of "but muh pancake".  Flanker and Fulcrum have it too, and they both have LERXs.  F-15s inlets nod with AoA and act similar to Su-33 canards in managing the airflow over the broad, flat, lift making body.  Does the Pancake make lift?  YES!  But the AoA where it becomes effective is as/after the wings stall.

 

Thank you @Spurts,

I see, when the Tomcat has its wings fully span forward, its lift geometry resembles more akin let's say a U2 aircraft, than a Mirage 2000 with delta wings, something like that ?

 

The value for the MiG-29A makes any sense for you also?

 

Regarding the Tomcat's "pancake area", many people do not undervalue it, and claim a considerable percentage of the airframe's total lift come from it...

Edited December 8, 2021 by Top Jockey

[Spurts]

The MiG value is in the ballpark of what I would expect but it's not a value I have been able to verify.

As to the pancake and "considerable percentage of the airframes total lift"... well... 

Here is a bit I wrote a few years back.  View topic - Wing Loading: You keep using that term.... - Technology (f-16.net)

That post was about total lift generation, not drag due to lift.

[Top Jockey]

1 hour ago, Spurts said:

The MiG value is in the ballpark of what I would expect but it's not a value I have been able to verify.

As to the pancake and "considerable percentage of the airframes total lift"... well... 

Here is a bit I wrote a few years back.  View topic - Wing Loading: You keep using that term.... - Technology (f-16.net)

That post was about total lift generation, not drag due to lift.

 

Interesting read.

[Kefa]

I understand the F-14 Clmax is over 2.  Point being we  have its +/-specific excess power plots also.  If you look at the F-14B (I haven't figured it for the A yet) at 5,000ft turn chart w/4 sparrow/4 sidewinder 55,620lbs.

  Attempting to "ride" its max lift curve level (in actuality  we would be a few degrees slightly in front of it -or we depart the jet); From  .5mach approx 303KCAS and 6.5G the estimated negative specific excess power is (my own estimate, since chart stops at -800) around -1200fps.  If we "ride" the top of that  max lift line all the way down to  .2mach approx 120KCAS and 1.8G, the negative specific excess power is now at -100fps.  In measuring from -1200fps/303KCAS/6.5G to -100fps/120KCAS/1.8G the F-14B can only complete 127 degrees of turn before basically stalling out or having to terminate its turn.  Even if you extrapolate the curve to 7.5G and estimated -1500fps at .54mach the F-14B now only completes 142degrees of turn before basically stalling out and having to end turn.   This certainly does not equate to having optimum turn performance.  And I don't even know if the jet can actually fly that slow (down to 120KCAS in a turn), perhaps I should have stopped at just 150KCAS, but I decided to compute it even further down the max lift line.  I would also expect the A to have completed less of a turn, while at a slightly smaller radius than the B. 

The point being is that jets with limiters while in essence never reach Clmax, they however will complete more degrees of turn at the cost of a slightly larger turn radius.  Perfect example is Dassault Rafale, and early F-16A. 

 

Now problem here is the only charts that include all the negative specific excess power lines is the Hellenic F-16 manual.  Both Tomcat manuals stop at -800fps, yet the A has a few chart that actually go beyond -800fps I think.  The F-15 does not include them, and to my knowledge nor do the Flanker or Fulcrum.  

 

While the  F-14A 1977 SAC has one chart, a VN diagram for 35,000ft. That measures peak specific excess power loss to -36kps at 1mach and 5.5G.  If we convert that to fps it is about -1837 if I am not mistaken.  

 

Edit: stopping the turn to -200fps/at max lift or to basically .26mach, now the jet only completes 85 degrees of turn that is if you start turn at 6.5G and 303KCAS.  If you start turn at 7.5G and .54mach Tomcat completes almost 100 degrees of turn, again, ending at .26mach.

 

 

 

Edited December 9, 2021 by Kefa

[captain_dalan]

6 hours ago, Cmptohocah said:

1- If you are below your max sustained turn rate (let's forget about corner speed for now), the adversary will get its nose on you eventually - it's just geometry.
2- If you trade KNOTS for angles, there is absolutely no reason for the enemy to keep sustained turn rate and they too will trade speed for angles 
3-  but now they have more energy then you. Best you can do in this situation is try to force a one-circle fight or an overshoot
4- but this is not likely to happen with Archers.

1- He will......if i get stuck in lag. But what's stopping me from relaxing or unloading, getting my knots back, and doing it all over again. The outcome depends on what happens faster, me getting enough knots back, or him completing a turn which he starts at a position of disadvantage. 
2- But the entire line of reasoning behind the example is to illustrate why you should NOT sustain at all times. If he decides to bleed or go out of plane, then there is no sustaining, ergo, no need for the illustration, right?
3- They may, they may not. It's not a given. Once both sides start playing the energy game, then who even manages his/her transitions better will come on top. And it will also be AC specific, as not all planes perform the same along the entire envelope
4- at this point we are purely academic and removed from the scope of the mental exercise, but i'll indulge you......why not? If you go one circle in such a way that you will get inside the Archer WEZ, you have just completed one way of surviving the merge with the R-73 equipped platform. It may not the be the best way, but it is A way. 

[captain_dalan]

6 hours ago, Top Jockey said:

 

2. I suppose more power is important to overcome drag also when turning > gaining / maintaining a little bit more speed on that turn > allow for pull more on the stick and maintaining more G's at a given speed ?

(... and the jet which can pull more G's for the same speed than the other, will have a superior turn rate.)

4. on the Sustained Turn Rate :

- instead, regarding the MiG-29A, the STR is an aspect where I was expecting it to be stronger, given the characteristics I mentioned at the other post.

 

5.  I guess, if the MiG-29A was instead an unstable design / relaxed static stability like the F-16, some aspects of its performance would be better... and amongst several details, it would have to get its center of gravity moved further aft, get a FBW, etc.

 

6. Supposing other important parameters being similar, wouldn't an airframe with a lower wing loading and better lift coefficient allow for maintaining more G's while turning, for the same speed, than a 'inferior' airframe ?

 

2. (and 3) the difference can (and in the case of the F-14) is negligible. And most aircraft are designed with certain parameters and performance in mind. But that is far beyond the scope of this topic i think.

4. It is stronger when compared to its direct competitor the F-16. Even though similar, it's STR per mach is better for lower airspeeds. I don't think you can expect one plane to be better in an arbitrary metric then all the other planes, along the entire envelope. Especially when comparing similar levels of technologies. 

5. I don't think relaxed stability is universally better as such. It does provide access to parts of the envelope that may not be available otherwise. But EVERY design is a compromise, and the choice of the airfoil, the geometry of the inlets, the power curve of the engines.....they all will play a part in the end product. And that product will be dynamic in nature, which leads us to:

6. I think you are relying to much on static properties (again) to quantify a highly dynamic process. Is a sail better lifting body then a 2x4? Of course it is. But that doesn't really resolve our conundrum now, does it? Better lift coefficient you say, but better at what angle of attack? As mentioned above, maintaining or sustaining g's (a turn) is a state where the excess power is zero, that is, the power of the engines is in a state of equilibrium with the total drag produced for a desired lift (g-force). Two planes can have same ratio between lifting surface and total weight (lift loading) but very different shapes of wings. In fact, they most certainly will. And even the airfoil used will have vastly different properties, that will result in very different performance at both different angles of attack and different airspeeds. There is no one perfect wing. If there was, every plane would have been designed with it. 

[Dell_Murrey-RUS]

15 часов назад, Top Jockey сказал:

Didn't imagine the Su-27's gun could jam if shot when pulling over 4 G's.

And why design a gun for overloads above 4G ?

The main range of close air combat speeds about 550-1100 km/h. At such speeds, an overload above 4 G will not allow you to aim, because the aiming mark will be outside the HUD field.

About Su-27, you need to understand the following:
- statical unstability in the longitudinal channel;
- advanced airframe aerodynamics (integral concept);
- high wing and body lift (Cy) with nice K (L/D) factor for heavy fighter;
- advanced wing mechanization;
- adequate drag coefficient (Cx) at AoA = 0-15 degrees.

And all this is in the operational speeds of air combat.

MiG-29 can't demonstrate such characteristics, its advantage is greater simplicity and lower price per copy and ideology of use (front-line fighter). One of its main advantages is the rapid acceleration of low AoA and increased "agility/edge" when performing maneuvers. But practice shows that in group air battles, this does not affect the percentage of victories at all. And the probability of meeting 1 on 1 in a duel is approaching zero.

[Top Jockey]

9 hours ago, captain_dalan said:

2. (and 3) the difference can (and in the case of the F-14) is negligible. And most aircraft are designed with certain parameters and performance in mind. But that is far beyond the scope of this topic i think.

4. It is stronger when compared to its direct competitor the F-16. Even though similar, it's STR per mach is better for lower airspeeds. I don't think you can expect one plane to be better in an arbitrary metric then all the other planes, along the entire envelope. Especially when comparing similar levels of technologies. 

5. I don't think relaxed stability is universally better as such. It does provide access to parts of the envelope that may not be available otherwise. But EVERY design is a compromise, and the choice of the airfoil, the geometry of the inlets, the power curve of the engines.....they all will play a part in the end product. And that product will be dynamic in nature, which leads us to:

6. I think you are relying to much on static properties (again) to quantify a highly dynamic process. Is a sail better lifting body then a 2x4? Of course it is. But that doesn't really resolve our conundrum now, does it? Better lift coefficient you say, but better at what angle of attack? As mentioned above, maintaining or sustaining g's (a turn) is a state where the excess power is zero, that is, the power of the engines is in a state of equilibrium with the total drag produced for a desired lift (g-force). Two planes can have same ratio between lifting surface and total weight (lift loading) but very different shapes of wings. In fact, they most certainly will. And even the airfoil used will have vastly different properties, that will result in very different performance at both different angles of attack and different airspeeds. There is no one perfect wing. If there was, every plane would have been designed with it. 

 

4. Well, something at the least !

By the way, might one of the reasons for that (at slower speeds) being the F-16's AoA limiter ?

 

5. Relaxed stability might not be universally better (I don't know), but according other members explanations, it is one of the motives which allows the Su-27 to pull a little bit more G's at slower speeds than the MiG-29, as it will need less AoA to pull the same G's.

 

(jumping some numbers)

8. On the Fulcrum, the issue is me managing my expectations (created through several years - even before internet, from several media sources, sims, etc.), which surely frequently augmented and took to "legendary" levels the Fulcrum's real life maneuverability.

 

The best example I can give, for my wrong expectations on the real life MiG-29's ACM capabilites is :

 

- take the F-15C's current flight model in DCS;

- go to F2 external view and observe the Eagle's nose authority / pitch rate; and freedom of movement (without the FCS also commanding a pitch-down order like in the MiG-29 when in high AoA); observe also the Eagle's apparent very good sustained turn rates at a big part of the speed envelope ;

- also in F2 external view (with bottom info bar) try Sustained Turn Rates at different airspeeds (near sea level for starters), and watch as it indeed looks fairly quick travelling around the turn circle, in praticaly any speed range - even below 300 kts airspeeds...

 

... now paste exactly that flight model on the MiG-29A, and that was how I always imagined it to behave / maneuver in real life.

 

9. Concluding, I will ask you the same question I asked to Ironhand and Dell_Murrey-RUS, in this way :

Forgeting combat tactics perspective, but purely airframe technical comparison ; would you qualify the Su-27S as a better dogfighting airframe than the MiG-29A, or not at all ?

[Top Jockey]

1 hour ago, Dell_Murrey-RUS said:

1. And why design a gun for overloads above 4G ?

2. The main range of close air combat speeds about 550-1100 km/h. At such speeds, an overload above 4 G will not allow you to aim, because the aiming mark will be outside the HUD field.

3. About Su-27, you need to understand the following:
- statical unstability in the longitudinal channel;
- advanced airframe aerodynamics (integral concept);
- high wing and body lift (Cy) with nice K (L/D) factor for heavy fighter;
- advanced wing mechanization;
- adequate drag coefficient (Cx) at AoA = 0-15 degrees.

And all this is in the operational speeds of air combat.

4. MiG-29 can't demonstrate such characteristics, its advantage is greater simplicity and lower price per copy and ideology of use (front-line fighter). One of its main advantages is the rapid acceleration of low AoA and increased "agility/edge" when performing maneuvers. But practice shows that in group air battles, this does not affect the percentage of victories at all. And the probability of meeting 1 on 1 in a duel is approaching zero.

 

1. A gun shot at just 4 G's doesn't look that much high a load for me, and it offers more possibilities as seen in other jet fighters ?

 

2. Ok, for the Su-27 the aiming mark will be out of the HUD in that situation.

But for instance other fighters like F-16, do account also for even more lead pull gun shots (because of higher G's possibility), in their design, they have their gun more canted upwards, allowing to place the gun boresight right at the top of the HUD, sharper ballistic trajectory, etc...

 

3. Advanced wing mechanization - don't know what this is.

Advanced airframe aerodynamics (integral concept) - would be more interested to know in which key aspects it is superior to the MiG-29A's, if possible.

 

4. On the MiG's agility, indeed it shows a more agile pitch rate than the Su-27.

Sure, i've never looked to compare 2 different airframes in order to access their prevailing in war / combat situation, and obviously the 1 v 1 duel eventuality is very limited, neither it interests to me.

What I search for as my main interest is, purely in a physical / aerodynamic capability, which one from 2 different airframes would be 'superior' technicaly speaking.

... and in that regard you were very clear already on the other post: the Su-27.

Edited December 9, 2021 by Top Jockey

[Dell_Murrey-RUS]

2 часа назад, Top Jockey сказал:

5. Relaxed stability might not be universally better (I don't know), but according other members explanations, it is one of the motives which allows the Su-27 to pull a little bit more G's at slower speeds than the MiG-29, as it will need less AoA to pull the same G's.

Wow wow! No, it's a big mistake.

Statical unstability in the longitudinal channel need to reduce losses on horizontal stabilizers and at the same time increase the overall lifting force. The AoA of the stabilizers are greatly reduced and practically do not create resistance to the air flow. Therefore, the Su-27 in horizontal flight often has negative AoA on the stabilizers. Classical design stabilizers stay by airflow.

1 час назад, Top Jockey сказал:

1. A gun shot at just 4 G's doesn't look that much high a load for me, and it offers more possibilities as seen in other jet fighters ?

GSh-30-1 not a gun. That's a large cannon with 30mm, projectile weight 390 grams. Recoil when firing more than 7000 kg. Rate of fire 1500 rounds per minute. 4G is very good for GSh.

1 час назад, Top Jockey сказал:

2. Ok, for the Su-27 the aiming mark will be out of the HUD in that situation.

But for instance other fighters like F-16, do account also for even more lead pull gun shots (because of higher G's possibility), in their design, they have their gun more canted upwards, allowing to place the gun boresight right at the top of the HUD, sharper ballistic trajectory, etc...

It's another parameters of cannon.

1 час назад, Top Jockey сказал:

3. Advanced wing mechanization - don't know what this is.

Adaptive wing: https://bigenc.ru/technology_and_technique/text/4137890

Use translater.

1 час назад, Top Jockey сказал:

Advanced airframe aerodynamics (integral concept) - would be more interested to know in which key aspects it is superior to the MiG-29A's, if possible.

There are quite a few tricks. Here it is enough to compare the lift coefficients of the Su-27 and MiG-29 airframe and also compare the aerodynamic quality (K). The numbers speak for themselves.

1 час назад, Top Jockey сказал:

4. On the MiG's agility, indeed it shows a more agile pitch rate than the Su-27.

Yes, the Mig is faster, but with the same speed it loses energy in such maneuvers.
And it is not clear where such quick maneuvers can be useful in air battles.

[Top Jockey]

17 minutes ago, Dell_Murrey-RUS said:

5. Wow wow! No, it's a big mistake.

Statical unstability in the longitudinal channel need to reduce losses on horizontal stabilizers and at the same time increase the overall lifting force. The AoA of the stabilizers are greatly reduced and practically do not create resistance to the air flow. Therefore, the Su-27 in horizontal flight often has negative AoA on the stabilizers. Classical design stabilizers stay by airflow.

 

1. GSh-30-1 not a gun. That's a large cannon with 30mm, projectile weight 390 grams. Recoil when firing more than 7000 kg. Rate of fire 1500 rounds per minute. 4G is very good for GSh.

 

2. Adaptive wing: https://bigenc.ru/technology_and_technique/text/4137890

Use translater.

 

3. There are quite a few tricks. Here it is enough to compare the lift coefficients of the Su-27 and MiG-29 airframe and also compare the aerodynamic quality (K). The numbers speak for themselves.

 

 

5. I recal its importance has been highlighted to me by you, @bies and others already in the past.

When I wrote it might not be "universally better", I was quoting other members here.

 

1. Very interesting - such an heavy recoil i didn't imagine.

But if your target is a jet fighter pulling a hard turn, and the circumstances dictate you can only use the cannon, the option to shoot at more than 4 G's would be crucial...

 

2. Interesting.

3. The CL Max I've found around the web for MiG-29A and Su-27S, is respectively: 1.50 and 1.85 ... comparatively speaking both stand below the F-14 Tomcat's: 2.2 as informed by other member here yesterday - which surprised me.

[Youda]

On 12/8/2021 at 5:47 PM, captain_dalan said:

If you've seen the performance charts for the F-14A and F-14B, you'd see ...

@captain_dalan Do you have them? Can you post them?

[Dell_Murrey-RUS]

2 часа назад, Top Jockey сказал:

5. I recal its importance has been highlighted to me by you, @bies and others already in the past.

When I wrote it might not be "universally better", I was quoting other members here.

Oh, yes, ok.

I have met very few people who could explain what a statically unstable airplane in a longitudinal channel is in its practical application. They could not explain in simple words what it gives the glider.

2 часа назад, Top Jockey сказал:

1. Very interesting - such an heavy recoil i didn't imagine.

But if your target is a jet fighter pulling a hard turn, and the circumstances dictate you can only use the cannon, the option to shoot at more than 4 G's would be crucial...

This is utopia. In fact, you write about shooting "under the hood". And this is not targeted shooting. From the history of jet aviation of the 4th generation, I do not recall such cases.

If this is one case per 100,000, then this probability can be ignored.

2 часа назад, Top Jockey сказал:

2. Interesting.

Here you can see how the adaptive wing works on the Su-27 (view from Earth), it is well implemented in the DCS. There are many views of slats (LEX) and flaps at the moments of performing various maneuvers at different speeds and AoA. And the operation of horizontal stabilizers, the installation of negative angles, diff working and etc.

2 часа назад, Top Jockey сказал:

3. The CL Max I've found around the web for MiG-29A and Su-27S, is respectively: 1.50 and 1.85 ... comparatively speaking both stand below the F-14 Tomcat's: 2.2 as informed by other member here yesterday - which surprised me.

And what is surprising here?

And what is the K (L/D) factor for F-14?

[Top Jockey]

27 minutes ago, Dell_Murrey-RUS said:

...

And what is surprising here?

And what is the K (L/D) factor for F-14?

 

My surprise is the comparatively high value for the F-14, and how can a more modern design like the Su-27 still stay considerably below regarding CL max...

I don't have the slightest idea of the K (L/D) value for any of them.

[Spurts]

L/D for the F-14 is up to 15.  

[Dell_Murrey-RUS]

11 часов назад, Top Jockey сказал:

My surprise is the comparatively high value for the F-14, and how can a more modern design like the Su-27 still stay considerably below regarding CL max...

There's nothing surprising about that. Some individual parameters of old aircraft may exceed those of new ones. The capabilities of any aircraft must be evaluated in a set of parameters. Then the surprise will pass. There are a lot of tricks and nuances in this scene.